Glare filter for head lamp



J. A. HOLMAN GLARE FILTER FOR HEAD LAMP Oct. 7,1958.

2 Sheets-Sheet 1 Filed .July 9, 1954 Fig'5 INVENTOR John A. Holman Fig.4

Fig. 3

ATTORNEYS Oct. 7,1958.

Filed July 9, 1954 J. A. HOLMAN 2,855,500

' GLARE FILTER FOR HEAD LAMP 2 Sheets-Sheet 2 INVENTOR John A HolmanATTOR EYS a 2,855,500 Patented Oct. 7, 1958 GLARE FILTER FOR HEAD LAMPJohn A. Holman, Dallas, Tex.

Application July 9, 1954, Serial No. 442,361

3 Claims. (Cl. 240-46.45)

This invention relates to new and useful improvements in anti-glaremeans for automobile head lamps.

A conventional head lamp includes a light source or filament, a concavereflector and a coacting lens, with the filament being contained by aremovable lamp bul-b or being prefocused and fixed directly within thereflector and with the lens being removably attached or permanentlysealed to said reflector to provide a so-called sealed beam lamp.Usually, the reflector is of the parabolic type for directivelyreflecting the light rays emitted by the filament in a concentratedbeam, while the lens is of the diffusing type having a plurality ofupright substantially parallel major prisms or flutes for refracting therays of the beam horizontally so as to spread said beam laterally ortransversely. Each upright prism or flute is divided into small sectionsor minor prisms for bending or refracting the rays of the beamdownwardly and the minor prisms are arranged in substantially parallel,transverse rows and may be asymmetrical. As a result, the beam is of awidth much greater than its height and is primarily confined within aplane parallel to the horizontal axis of the lamp.

Although the lens prisms are designed to coact with the reflector andfilament in providing a beam of parallel light rays, the coaction is notperfect because of the multiplicity of light rays emitted by thefilament in spaced relation to the true focal point. A large portion ofthe light rays are directed or reflected upwardly above the horizontalplane of the beam and cannot be refracted downwardly to a sufiicientextent by the minor downbending prisms. It is these uncontrolled rayswhich cause upward blinding glare and which strike the eyes of driversof approaching automobiles as well as rear view mirrors of automobilesimmediately in front of the head lamps.

It has been found that the objectionable or upwardlydirected rays passthrough the upper portions of the minor prisms at and above thehorizontal axis of the lamp and, being relatively thin and having littlerefraction properties, said upper portions cannot bend said raysdownwardly to the horizontal plane of the beam. Also, it has been foundthat the minor prisms at the upper, central portion of the lens causesubstantially all of the glare and that the light rays passing throughthe lower prisms arc confined within or directed below the horizontalplane of the beam, while the laterally-disposed prisms direct the rayslaterally and there are fewer rays passing through saidlaterally-disposed prism. Therefore, the objectionable glare of anautomobile head lamp may be substantially eliminated by filtering orotherwise obscuring the light rays passing through the upper and/ orrelatively thin portions of the minor prisms in the upper, centralportion of the lens.

One-object of the invention is to provide improved anti-glare means forautomobile head lamps and other lamps having diffusing lenses wherebysubstantially all lamps.

Another object of the invention is to provide improved means forsubstantially eliminating the glare of automobile head lamps withoutimpairing the efliciency of the lamps or creating excessive heat whichmight cause failure of the light source or changing the construction ofsaid lamps, their adjustment or operation.

A particular object of the invention is to provide improved means formaterially reducing the glare of head lamps whereby it is unnecessary todim or depress the light beam for passing approaching automobiles andwhereby the head lamps are more eflicient in fog, rain, sleet, snow anddust conditions.

An important object of the invention is to provide improved means forsubstantially eliminating the glare of automobile head lamps havingdiffusing lenses by obscuring the upper or relatively thin portions ofthe minor down-bending prisms in the upper, central portions of thediffusing lenses whereby the light beams of anti-glare means, of thecharacter described, which is capable of being used in any lamp having adiffusingv lens of the type formed with substantially parallel prisms orflutes for spreading the light rays transversely of the flutes anddivided into minor light-bending prisms for refracting said rayslongitudinally of said flutes.

A construction designed to carry out the invention will be hereinafterdescribed together with other featuresof the invention.

The invention will be more readily understood from a reading of thefollowing specification and by reference to the accompanying drawings,wherein examples of the invention are shown, and wherein:

Fig. 1 is an elevational view of a head lamp having a lens provided withanti-glare means in accordance with the invention, Fig. 2 is a sideelevational view of the lamp with the lens in transverse, verticalsection and taken on the line 2-2 of Fig. 1,

Fig. 3 is an enlarged, horizontal, cross-sectional view, taken on theline 33 of Fig. 1, and showing one-half of the lens,

Fig. 4 is a view, similar to Fig. 3, showing a modified form of theinvention,

Fig. 5 is a view, similar to Fig. 4, of another modification,

Fig. 6 is an, enlarged, side elevational view, partly in section, of thelamp and showing the function of the antiglare means,

Fig. 7 is an enlarged, transverse, vertical sectional view of a portionof a conventional lens without the antiglare means, and

Fig. 8 is an enlarged, transverse, vertical sectional view of a typicalfilament and a portion of a parabolic reflector.

In the drawings, the numeral 10 designates an automobile head lamp whichincludes a reflector 1-1, a light source or filament 12 and a lens 13.Preferably, the lamp the filament contained by or mounted between .saidreflector and lens and a terminal 14 projects rearwardly from the axialportion of said reflector.

shown, it is pointed out the invention is applicable to 3.

Although not lamp having a separable lens and reflector with thefilament mounted in a removable bulb. The reflector 11 is of theparabolic type for reflecting the light rays emitted by the filament 12in a concentrated beam of substantially parallel rays, while the lens 13is of the diffusing type having a plurality of upright "major prisms orflutes 15 formed in its inner surface for spreading the rays laterallyor transversely of the horizontal axis of the lamp.

Usually, the major prisms are substantially parallel, vertical. andequally-spaced and the resulting beam is of generally oval shape ofgreater width than height. Each prism 15 is substantially concave intransverse, cross-section and includes a longitudinal groove or valley16 with marginal ridges 17 between adjacent prisms (Figs. 3-5 Forbending the rays downwardly, each major prism is divided into aplurality of small sections or minor downbending prisms 1 8 which arearranged in substantially parallel, transverse rows '(Figs. 1, 2, 6 and7). Ordinarily and necessarily, the minor prisms decrease in thicknessupwardly so as to provide downwardly-facing, transverse risersorhorizontal shoulders 19 between adjacent minor prisms. The foregoingconstruction is more or less conventional and in itself forms no part ofthe present invention.

As shown by the broken lines 20 in Fig. 7, the light rays passingthrough the lower or relatively thick portions of the prisms 18 arerefracted or bent downwardly. Since the upper or relatively thinportions of the prisms have little refracting properties, the light rayspassing therethrough are not refracted but are merely deflected and aretransmitted in substantially parallel relation to their paths ofincidence as indicated by the broken lines 21. As aresult, if theincident rays are directed upwardly, as shownin Fig. 7, the transmittedrays are directed upwardly and are not bent downwardly into parallelrelation to the horizontal axis of the lamp so as to be confined to thehorizontal plane of the beam. Although the reflector 11 is adapted toreflect the rays in a concentrated beam, the very size of the filament12 prevents the obtaining of perfect results. As shown by the brokenlines 22, 23 and 24 in Fig. 8, every point on the reflector receiveslight rays from a multiplicity of points on the filament and said rayshave an angular, non-parallel relationship. Manifestly,v all of theserays do not emanate from the true focal point and cannot be accuratelycontrolled by the reflector. In addition, there are a large number ofrays emitted forwardly by the filament directly through the lens andsome of these rays are directed upwardly and pass through the upper orrelatively-thin portions of the prisms 18.

Since it is impossible to refract or otherwise control theseupwardly-directed light rays by a lens of conventional construction,anti-glare means has been provided for the upper or relatively-thinportions of the minor prisms so as to obscure said rays. As shown by thenumeral 25 in Figs. 1, 2 and 6, the anti-glare means is required only atthe upper, central portion of the lens 13 because the rays passingthrough the lower and laterally-disposed minor prisms are less intenseor fewer in quantity and/or are confined within or directed below orlaterally of the horizontal plane of the beam. Also, the anti-glaremeans is of upwardly-decreasing length transversely of the lens, wherebythe uppermost means 25a is of least length and the lowermost means 25cis of greatest length (Fig. 1). Since the lowermost anti-glare means isdisposed at substantially the horizontal axis of the lamp, said meansmay be relatively narrow or of less height than the other anti-glaremeans. The anti-glare means is adapted to obscure or obstruct the lightrays passing through theupper or relatively-thin portions of the minorpn'sms 18 as shown by the broken lines 26 in Fig. 6 without interferingwith the passage of rays 27 through the lower or relatively thickportions of said prisms.

Although the anti-glare means may be formed of opaque or lightobstructing material, such as paint, vitrous or metallic material, saidmeans may be translucent so as to merely filter or retard theobjectionable rays. The filtering or light-retarding means may be in thenature of pigmentation, colored glass or plastic or retracting prisms.Preferably, the anti-glare means is applied to the inner surface of thelens so as to retain the continuity of its external contour, but may beformed in or made integral with said lens. Although satisfactory resultsmay be obtained by supplementary prisms, it is more economical to filteror otherwise obscure the rays. As shown by the numeral 28 in Fig. 3, theanti-glare means need be applied only to the valleys 16 of the uprightflutes 15 since the ridges 17 refract the rays laterally. The numeral 28also indicates that the anti-glare means is in the nature of paint orother suitable material applied directly to or forming a part of saidlens. For ease of application, the anti-glare means for each transverserow of minor prism portions may be continuous and cover the ridges aswell as the valleys as shown by the numeral 29 in Fig. 4, such as stripsof colored glass or plastic or other filtering or translucent material.In Fig. 5, the anti-glare means is shown in the form of a strip 30 ofmetal or other opaque or light obstructing means suitably attached tothe lens in overlyingrelation to the valleys and ridges of the upper orrelatively-thin portions of the minor prisms. Irrespective of its form,the anti-glare means is disposed in spaced, transverse rows conformingto the transverse rows of minor prisms and the spacing between the upperor relatively-thin portions of said prism rows.

If desired, the filament 12 may be shielded from direct view by thedriver ofan approaching automobile by means 31 overlying the lower orrelatively thick portions of the lowermost anti-glare means (Figs. 1, 2and 6). The means 31 may be formed of the same material as theanti-glare means and may have little height so long as it filters orotherwise obscures the direct, axial rays of the filament indicated bythe numeral 32 in Fig. 6.

From the foregoing, it is readily apparent that novel means has beenprovided for substantially eliminating the objectionable glare ofautomobile head lamps without impairing the efliciency of the lamps orcreating excessive heat which might result in premature failure of thefilament. The vast majority of the light rays are utilized due to therelatively-small area of the anti-glare means which only obscures theobjectionable rays. Although filtering or translucent means is preferreddue to les interference with heat transfer, it is possible to employmetal or other opaque or light-obstructing material. It has been foundthat it is unnecessary to dim or depress the beam for passingapproaching automobiles and that the lamps are more elficient in fog,rain, sleet, snow and dust conditions since there are no appreciablequantities of rays directed upwardly above the horirzontal plane of saidbeam. Another advantage resides in the fact that the application and useof the invention does not alter the construction, operation oradjustment of the lamps. It is noted that the invention is applicable tolamps other than but similar to head lamps.

The foregoing description of the invention is explanatory thereof andvarious changes in the size, shape and materials, as well as in thedetails of the illustrated construction may be made, within the scope ofthe appended claims, without departing from the spirit of the invention.

What I claim and desire to secure by Letters Patent is:

1. A headlamp having a lens provided with a plurality of transverselyextending rows of prisms on its inner surface, said prisms being alsoarranged in vertical parallel rows, each of said prisms having a;relatively thick base and a relatively thin upper-portion, andanti-glare means obscuring glare from the upper section of the lens,said last named means comprising a. plurality of light obstructingelements, said elements being disposed in vertiw cally spacedtransversely extending rows conforming to the vertically spacedtransversely extending rows of prisms and to the spacing between thethin upper portions of said prism rows, said elements overlying intransverse rows said upper portions of the prisms at the top half of thelens and such transverse rows increasing in height from the middle ofthe lens to the top of the lens.

2. A head lamp having a lens provided with a plurality of transverselyextending rows of prisms on its inner surface, said prisms being alsoarranged in vertical parallel rows, each of said prisms having arelatively thick base and a relatively thin upper portion, andanti-glare means obscuring glare from the inner and top part of theupper section of the lens and passing unobscured light from theperipheral sides of the upper section of the lens, said last named meanscomprising a plurality of light obstructing elements, said elementsbeing disposed in vertically spaced transversely extending rowsconforming to the vertically spaced transversely extending rows ofprisms and to the spacing between the thin upper portions of said prismrows, said elements overlying in transverse rows said upper portions ofthe prisms at the top half of the lens and such transverse rowsincreasing in length from the top of the lens down to the middle of thelens and increasing in height from the middle of the lens to the top ofthe lens.

3. A head lamp having a lens provided with a plurality of transverselyextending rows of prisms on its inner surface, said prisms being alsoarranged in vertical parallel rows, each of said prisms having arelatively thick base and a relatively thin upper portion, andanti-glare means obscuring glare from the inner and top part of theupper section of the lens and passing unobscured light from theperipheral sides of the upper section of the lens, said last named meanscomprising a plurality of light obst-ructing elements, said elementsbeing disposed in vertically spaced transversely extending rowsconforming to the vertically spaced transversely extending rows ofprisms and to the spacing between the thin upper portions of said prismrows, said elements overlying in transverse rows said upper portions ofthe prisms at the top half of the lens and such transverse rowsincreasing in length from the top of the lens down to the middle of thelens and increasing in height from the middle of the lens to the top ofthe lens while terminating in spaced relation with the margins of saidlens.

References Cited in the file of this patent UNITED STATES PATENTS1,899,964 Hughes Mar. 7, 1933 2,260,736 Benton Oct. 28, 1941 2,277,563Scott et a1. Mar. 24, 1942 FOREIGN PATENTS 11,054 Great Britain 1908115,907 Austria Ian. 25, 1930

